Sensor device

ABSTRACT

A sensor unit includes a pressure sensor, an acceleration sensor and a signal-processing circuit, which are disposed on the bottom surface of a lead to form a line in the longitudinal direction of the sensor unit. The pressure sensor and the acceleration sensor are disposed at respective symmetrical positions with respect to the center of the signal-processing circuit in the longitudinal direction of the sensor unit. Each of the pressure sensor and the acceleration sensor has substantially the same height dimension. The sensors, the signal-processing circuit and the lead are sealed with a molded body, in such a manner as to allow lead terminals of the lead to protrude outside the molded body. The signal-processing circuit is operable, based on a signal from the acceleration sensor, to control the ON/OFF action of the pressure sensor.

TECHNICAL FIELD

The present invention relates to a sensor unit for measuring a pluralityof physical quantities.

BACKGROUND ART

Heretofore, in a measuring system where it is required to measure aplurality of different types of physical quantities or a plurality ofthe same type of physical quantities different in detection range, aplurality of separately-packaged sensors have been used. In this case,the plurality of separately-packaged sensors have to be mounted on acircuit board individually. This involves the need for assuring a largespace (area) for mounting these physical-quantity sensors in the circuitboard, which leads to undesirable increases in size, complexity and costof the measuring system.

As one measure against this problem, it is conceivable to incorporate aplurality of sensors into a single package. For example, the followingPatent Publication 1 discloses a compound sensor unit having a pressuresensor for detecting a pressure and a temperature sensor for detecting atemperature which are incorporated into a single package.

Patent Publication 1: Japanese Patent No. 3149957 (FIG. 2)

DISCLOSURE OF INVENTION Problems to Be Solved by Invention

A conventional compound sensor unit as disclosed, for example, in PatentPublication 1 can solve the above problem caused by mounting a pluralityof sensors on a circuit board individually. However, the conventionalcompound sensor unit involves a problem concerning higher powerconsumption because it is designed to drive the pressure sensor and thetemperature sensor independently. For example, a sensor-driving batteryto be equipped in a measuring system is required to have a largercapacity.

In view of the above conventional problem, it is an object of thepresent invention to provide a sensor unit capable of reducing a space(area) required for mounting a plurality of sensors for measuringphysical properties, and reducing the electric power required fordriving these sensors.

Means for Solving Problems

In order to achieve the above object, the present invention provides asensor unit including a lead, a plurality of physical-quantity sensors,a signal-processing circuit and a molded body. The lead has edges formedas lead terminals serving as input/output terminals. Each of thephysical-quantity sensors is disposed relative to the lead and adaptedto measure a physical quantity. The signal-processing circuit isdisposed relative to the lead and adapted to process a signal from eachof the physical-quantity sensors. The molded body is made of a plasticmaterial, and formed to seal the lead, the physical-quantity sensors andthe signal-processing circuit in such a manner as to allow the leadterminals to protrude outside the molded body. The signal-processingcircuit is operable, based on the signal from at least one of theplurality of physical-quantity sensors, to control the ON/OFF action ofthe remaining physical-quantity sensors.

According to this sensor unit, as compared to the conventional measuringsystem where a plurality of physical-quantity sensors are mountedseparately, the space (area) required for mounting the physical-quantitysensors can be reduced. In addition, the signal-processing circuit isoperable, based on the signal from at least one of the physical-quantitysensors, to control the ON/OFF action of the remaining physical-quantitysensors, so that the need for constantly driving all of thephysical-quantity sensors can be eliminated to achieve lower powerconsumption. Thus, when a battery is incorporated in the sensor unit,there is no need to use a large-size battery having a larger capacity,and thereby the battery can be reduced in size.

In one embodiment of the present invention, the plurality ofphysical-quantity sensors include a pressure sensor and an accelerationsensor. In this case, the molded body is formed with a through-holeextending upward from a pressure-receiving portion of the pressuresensor and having an opening to the outside of the molded body. Thisthrough-hole defines a pressure-introducing passage which allows fluidcommunication between the outside of the molded body and thepressure-receiving portion. Alternatively, the plurality ofphysical-quantity sensors may include an acceleration sensor and arotational-angular-velocity sensor.

In the sensor unit including the pressure sensor and the accelerationsensor (hereinafter referred to as “pressure/acceleration sensor”), itis preferable that the pressure sensor, the acceleration sensor and thesignal-processing circuit are disposed to form a line in thelongitudinal direction of the sensor unit. In this case, the pressuresensor and the acceleration sensor may be disposed at respectivesymmetrical positions with respect to the center of thesignal-processing circuit in the longitudinal direction of the sensorunit. Further, each of the pressure sensor and the acceleration sensormay have substantially the same height dimension. According to thispressure/acceleration sensor, the respective thicknesses of the moldedbody on the underside of the pressure sensor and on the underside of theacceleration sensor are substantially equalized so that respectivestresses on the longitudinal opposite ends of the sensor unit arebalanced. This provides enhanced measurement accuracy.

Preferably, the pressure/acceleration sensor includes a flexible resininterposed between the acceleration sensor and the molded body. Theresin can suppress the deformation of the acceleration sensor to provideenhanced measurement accuracy.

In the pressure/acceleration sensor, the pressure-introducing passagemay include a plurality of small-diameter channels. This can preventforeign matter, such as foreign particles or dust, from getting into thepressure sensor. In addition, even if an excessive pressure isintroduced into the through-hole, the channels can reduce the shock dueto the pressure to prevent breakage of the pressure sensor.

In the pressure/acceleration sensor, the molded body may be integrallyformed with a tubular portion extending continuously from the edge ofthe opening of the through-hole to the outside of the molded body andhaving substantially the same inner diameter as that of thethrough-hole. For example, when the entire circuit board having thesensor unit mounted thereon is sealed with silicone resin or the like toprovide a moisture resistance thereto, the tubular portion can preventthe silicone resin or the like from getting into thepressure-introducing passage. The tubular portion can also preventforeign matter, such as foreign particles or dust, from getting into thepressure-introducing passage.

In the sensor unit of the present invention, each of the plurality ofphysical-quantity sensors may have substantially the same heightdimension. In this case, it is preferable that the molded body has afirst portion extending between each of the physical-quantity sensorsand an outer surface of the molded body on the side of the physicalquantity sensor and a second portion extending between the lead and anouter surface of the molded body on the side of the lead, wherein eachof the first and second portions has substantially the same thicknessdimension. This can reduce a thermal stress caused by the difference inlinear expansion coefficient between each of the physical-quantitysensors and the molded body made of a plastic material, to achieve areduced temperature dependence of the sensor unit.

In the sensor unit of the present invention, the molded body may have afirst portion covering the top-surface side of the lead and a secondportion covering the bottom-surface side of the lead, and the first andsecond portions may be formed to have different tapered shapes from oneanother so as to allow the respective volumes of the first and secondportions to be substantially equalized. This can reduce a thermal stresscaused by the difference in linear expansion coefficient between thelead and the molded body made of a plastic material, to achieve areduced temperature dependence of the sensor unit.

In the sensor unit of the present invention, at least one of theplurality of physical-quantity sensors and the signal-processing circuitmay be disposed, respectively, on the top and bottom surfaces of thelead in such a manner as to sandwich the lead therebetween. This allowsthe sensor unit to be reduced in size. In addition, the lead made ofmetal, such as iron-nickel alloy, is interposed between ICs of thesignal-processing circuit and the physical-quantity sensor. Thus, thelead can prevent the physical-quantity sensor from being adverselyaffected by noises generated from the signal-processing circuit.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a top plan view of a sensor unit according to a firstembodiment of the present invention.

FIG. 2 is a sectional view of the sensor unit in FIG. 1, taken along theline A-A.

FIG. 3 is a partial sectional view of the sensor unit in FIG. 1, takenalong the line B-B.

FIG. 4 is a bottom view of the sensor unit in FIG. 1.

FIG. 5 is a bottom view showing an internal wiring of the sensor unit inFIG. 1, wherein a lower molded body is removed therefrom.

FIG. 6 is a top plan view of a sensor unit according to a secondembodiment of the present invention.

FIG. 7 is a vertical sectional view of the sensor unit in FIG. 6.

FIG. 8 is a bottom view showing an internal wiring of the sensor unit inFIG. 6, wherein a molded body is removed therefrom.

FIG. 9 is a vertical sectional view of a sensor unit according to athird embodiment of the present invention.

FIG. 10 is a sectional view of a sensor unit according to a fourthembodiment of the present invention.

FIG. 11 is a top plan view of a sensor unit according to a fifthembodiment of the present invention.

FIG. 12 is a vertical sectional view of the sensor unit in FIG. 11.

FIG. 13 is a top plan view of a sensor unit according to a sixthembodiment of the present invention.

FIG. 14 is a vertical sectional view of the sensor unit in FIG. 13.

FIG. 15 is a vertical sectional view of a sensor unit according to aseventh embodiment of the present invention.

FIG. 16 is a vertical sectional view of a sensor unit according to aneighth embodiment of the present invention.

EXPLANATION OF NUMERALS

1: pressure sensor, 2: acceleration sensor, 3: signal-processingcircuit, 4: lead, A′: lead, 4 a: lead terminal; 4 a′: dummy leadterminal, 5: wire, 6: pressure-receiving portion, 7:pressure-introducing passage, 7 a: opening, 7 b: through-hole, 8: moldedbody, 8 a: upper molded body, 8 b: lower molded body, 9: pressure-sensormounting portion, 10: acceleration-sensor mounting portion, 11:signal-processing-circuit mounting portion, 12: tubular portion, 13:circuit board, 14: device mounting portion, 15: silicone resin.

BEST MODE FOR CARRYING OUT THE INVENTION

This application is based upon and claims priority to Japanese PatentApplication No. 2003-301907, the entire contents of which areincorporated herein by reference.

With reference to the accompanying drawings, various specificembodiments of the present invention will now be described. In theaccompanying drawings, a common component is defined by the samereference numeral.

FIRST EMBODIMENT

As shown in FIGS. 1 to 3, a sensor unit of the present invention may beused, for example, as a tire-air-pressure sensor. A sensor unitaccording to a first embodiment of the present invention includes apressure sensor 1, an acceleration sensor 2 and a signal-processingcircuit (signal processing IC) 3. The signal-processing circuit 3 isoperable, only when the acceleration sensor 2 detects acceleration, toactivate the pressure sensor 1. Each of the pressure sensor 1, theacceleration sensor 2 and the signal-processing circuit 3 is mounted onthe bottom surface of a lead 4. The signal-processing circuit 3 iswire-bonded or electrically connected to each of the pressure sensor 1and the acceleration sensor 2 through a plurality of bonding wires 5.

A portion of the lead 4 mounting the pressure sensor 1 is formed withone opening 7 a for transmitting an external pressure to apressure-receiving portion 6 formed in the pressure sensor 1. Thepressure-receiving portion 6 is composed, for example, of a diaphragm,and operable to detect a pressure. The lead 4 is covered and sealed witha molded body 8 made of a plastic material, in such a manner as to allowa plurality of lead terminals 4 a to protrude outside the molded body 8.The molded body 8 consists of an upper molded body 8 a located on theside of the top surface of the lead 4, and a lower molded body 8 blocated on the side of the bottom surface of the lead 4.

The upper molded body 8 a has a through-hole 7 b for allowing theopening 7 a to be exposed to the outside of the molded body 8. Theopening 7 a and the through-hole 7 b are in fluid communication with oneanother to define a pressure-introducing passage 7 for transmitting anexternal pressure to the pressure-receiving portion 6. Further, aflexible silicone resin 15 is disposed between the bottom surface of theacceleration sensor 2 and the lower molded body 8 b. This silicone resin15 suppresses the deformation of the acceleration sensor 2 due topressure.

As shown in FIGS. 4 and 5, the lead 4 is prepared by cutting andremoving a part of a lead frame made of metal, such as iron-nickelalloy. The lead 4 has a rectangular-shaped pressure-sensor mountingportion 9 for mounting the pressure sensor 1, a rectangular-shapedacceleration-sensor mounting portion 10 for mounting the accelerationsensor 2, a rectangular-shaped signal-processing circuit mountingportion 11 for mounting the signal-processing circuit 3, and the leadterminals 4 a. The pressure-sensor mounting portion 9, thesignal-processing circuit mounting portion 11 and theacceleration-sensor mounting portion 10 are integrally formed as asingle piece in such a manner that they are disposed to form a line inthe longitudinal direction of the sensor unit (right-left direction inFIGS. 4 and 5). Each of the pressure-sensor mounting portion 9 and theacceleration-sensor mounting portion 10 is integrally formed with two ormore of the lead terminals 4 a which protrude outward in the lengthwise(longitudinal) direction of the sensor unit. The sensor unit is alsoprovided with a plurality of leads 4′ which are formed separately fromthe lead 4 and electrically connected or wire-bonded to thesignal-processing circuit 3 through bonding wires 5. Each of the leads41 has a lead terminal 4 a. The lead terminals 4 a of the leads 4′protrude from the molded body 8 parallel to each other in the crosswisedirection of the sensor unit (a direction perpendicular to thelongitudinal direction of the sensor unit).

As seen in FIGS. 2 and 5, the pressure-sensor mounting portion 9, thesignal-processing circuit mounting portion 11 and theacceleration-sensor mounting portion 10 are disposed to form a line inthe longitudinal direction of the sensor unit. Further, in thepositional relationship in the longitudinal direction of the sensorunit, the pressure-sensor mounting portion 9 and the acceleration-sensormounting portion 10 are disposed at respective symmetrical positionswith respect to the center of the signal-processing circuit mountingportion 11. Furthermore, the height dimension or thickness h₁ of thepressure sensor 1 is set to be substantially equal to the heightdimension or thickness h₂ of the acceleration sensor 2. In this sensorunit, both the pressure sensor 1 and the acceleration sensor 2 aremounted on the bottom surface of the lead 4, and thereby the respectivebottom surfaces of these sensors 1, 2 are located at substantially thesame height position. This allows the respective thicknesses of thelower molded body 8 b on the underside of the pressure sensor 1 and onthe underside of the acceleration sensor 2 to be substantiallyequalized. Thus, respective stresses on the longitudinal opposite endsof the sensor unit can be balanced.

In the sensor unit according to the first embodiment, the pressuresensor 1 and the acceleration sensor 2 are integrally mounted on thelead 4, and sealed with the molded body 8. Thus, as compared to caseswhere the pressure sensor 1 and the acceleration sensor 2 are mounted ona circuit board individually, a required mounting space (area) on acircuit board can be reduced. In addition, the signal-processing circuit3 operable to control the ON/OFF action of the pressure sensor 1 inresponse to a signal from the acceleration sensor 2 can achieve lowerpower consumption. Thus, when a battery is incorporated in the sensorunit, the battery can be reduced in size. Furthermore, the deformationof the acceleration sensor 2 is suppressed by the silicone resin 15, andthe respective stresses on the longitudinal opposite ends of the sensorunit is balanced, so that the measurement accuracy of the sensor unitcan be drastically improved.

SECOND EMBODIMENT

With reference to FIGS. 6 to 8, a second embodiment of the presentinvention will be specifically described below. As shown in FIGS. 6 and7, a sensor unit according to the second embodiment includes a pressuresensor 1, an acceleration sensor 2, and a signal-processing circuit(signal processing IC) 3 having a function designed to activate thepressure sensor 1 only when the acceleration sensor 2 detectsacceleration. Each of the pressure sensor 1, the acceleration sensor 2and the signal-processing circuit 3 is mounted on the bottom surface ofa lead 4. The signal-processing circuit 3 is wire-bonded or electricallyconnected to each of the pressure sensor 1 and the acceleration sensor 2through two bonding wires 5. A portion of the lead 4 mounting thepressure sensor 1 is formed with one opening 7 a for transmitting anexternal pressure to a pressure-receiving portion 6 formed in thepressure sensor 1. The pressure-receiving portion 6 is composed, forexample, of a diaphragm, and operable to detect a pressure.

The lead 4 is covered and sealed with a molded body 8 made of a plasticmaterial, in such a manner as to allow a plurality of lead terminals 4 ato protrude outside the molded body 8. The molded body 8 consists of anupper molded body 8 a located on the side of the top surface of the lead4, and a lower molded body 8 b located on the side of the bottom surfaceof the lead 4. The upper molded body 8 a has a through-hole 7 b forallowing the opening 7 a to be exposed to the outside of the molded body8. The opening 7 a and the through-hole 7 b are in fluid communicationwith one another to define a pressure-introducing passage 7. An externalpressure is transmitted to the pressure-receiving portion 6 through thepressure-introducing passage 7.

FIG. 8 shows the sensor unit in the state before the lead 4 is sealedwith the molded body 8. The dotted line L₁ in FIG. 8 indicates a regionin which the molded body 8 is to be formed. The lead 4 is prepared bycutting and removing a part of a lead frame made of metal, such asiron-nickel alloy. The lead 4 has a rectangular-shaped pressure-sensormounting portion 9 for mounting the pressure sensor 1, arectangular-shaped acceleration-sensor mounting portion 10 for mountingthe acceleration sensor 2, a rectangular-shapedsignal-processing-circuit mounting portion 11 for mounting thesignal-processing circuit 3, and the lead terminals 4 a. The lead 4 isintegrally formed as a single piece in such a manner that one of twodiagonally-opposed corners of the signal-processing circuit mountingportion 11 is joined to one corner of the pressure-sensor mountingportion 9, and the other corner of the signal-processing-circuitmounting portion 11 is joined to one corner of the acceleration-sensormounting portion 10. Each of the outer corners of the pressure-sensormounting portion 9 and the acceleration-sensor mounting portion 10 isintegrally formed with the lead terminals 4 a protruding outward.

The sensor unit is also provided with a plurality of leads 4′ which areformed separately from the lead 4. These leads 4′ are electricallyconnected or wire-bonded to the signal-processing circuit 3 throughbonding wires 5. The leads 4′ are disposed to extend outward from thevicinity of the outer periphery of the signal-processing circuit 3 in aradial pattern. Lead terminals 4 a of the leads 4′ protrude outward fromthe molded body 8 parallel to each other in the lengthwise and crosswisedirections of the sensor unit. The lead terminals protruding from themolded body 8 are used as input/output terminals. Further, the moldedbody 8 is provided with one dummy lead terminal 4 a′ having no function.

In the sensor unit according to the second embodiment, the pressuresensor 1 and the acceleration sensor 2 are integrally mounted on thelead 4, and sealed with the molded body 8. Thus, as compared to caseswhere the pressure sensor 1 and the acceleration sensor 2 are mounted ona circuit board individually, a required mounting area on a circuitboard can be reduced. In addition, the signal-processing circuit 3operable to control the ON/OFF action of the pressure sensor 1 inresponse to a signal from the acceleration sensor 2 can achieve lowerpower consumption. Thus, when a battery is incorporated in the sensorunit, the battery can be reduced in size.

While the sensor unit according to the second embodiment employs acombination of a pressure sensor and an acceleration sensor, any othercombination of sensors may be used. For example, an acceleration sensorand a rotational-angular-velocity sensor may be combined, and thesignal-processing circuit may be designed to activate the accelerationsensor only when the rotational-angular-velocity sensor detectsrotational angular velocity. This sensor unit can be used, for example,in a vehicle, such as automobile, to detect a lateral accelerationrelative to a traveling direction only when a steering wheel is turnedto change the traveling direction. It is to be understood that any otherphysical-quantity sensor may be additionally incorporated in the sensorunit within the spirit and scope of the present invention.

THIRD EMBODIMENT

With reference to FIG. 9, a third embodiment of the present inventionwill be specifically described below. As shown in FIG. 9, a sensor unitaccording to the third embodiment, each of a pressure sensor 1 and anacceleration sensor 2 has substantially the same height dimension orthickness. That is, the respective bottom surfaces of the pressuresensor 1 and the acceleration sensor 2 are located at substantially thesame height position indicated by the dotted line L₂. Further, an uppermolded body 8 a and a lower molded body 8 b are formed such that theheight dimension ta (thickness) between the top surface of the uppermolded body 8 a and the top surface of a lead 4 becomes substantiallyequal to the height dimension tb (thickness) between the bottom surfaceof the lower molded body 8 b and each of the bottom surfaces of thepressure sensor 1 and the acceleration sensor 2. The remainingstructures are the same as those in the second embodiment, and theirdescription will be omitted.

In the sensor unit according to the third embodiment, each of thepressure sensor 1 and the acceleration sensor 2 has substantially thesame thickness, and the respective thicknesses of the molded body 8 onthe top-surface side and the bottom-surface side thereof aresubstantially equalized at the positions corresponding to the pressuresensor 1 and the acceleration sensor 2. This can reduce a thermal stresscaused by the difference in linear expansion coefficient between eachphysical-quantity sensor (sensor element), such as the pressure sensor 1and the acceleration sensor 2, and the molded body 8 made of a plasticmaterial, to achieve a reduced temperature dependence of the sensorunit. The above characteristic structure in the sensor unit according tothe third embodiment may be applied to each of the aforementioned firstand second embodiments and after-mentioned fourth to eighth embodiments.

FOURTH EMBODIMENT

With reference to FIG. 10, a fourth embodiment of the present inventionwill be specifically described below. In a sensor unit according to thefourth embodiment, a molded body 8 consists of an upper molded body 8 alocated on the upper side relative to a lead 4 and a lower molded body 8b located on the lower side relative to the lead 4, and the upper moldedbody 8 a and the lower molded body 8 b are formed to have differenttapered shapes from one another so as to allow the respective volumes ofthe upper and lower molded bodies 8 a, 8 b to be substantiallyequalized. The remaining structures are the same as those in the secondembodiment, and their description will be omitted.

In a sensor unit according to the fourth embodiment, each of the uppermolded body 8 a and the lower molded body 8 b has substantially the samevolume. This can reduce a thermal stress caused by the difference inlinear expansion coefficient between a metal material, such asiron-nickel alloy, constituting the lead 4, and a plastic materialconstituting the molded body 8, to achieve a reduced temperaturedependence of the sensor unit. The above characteristic structure in thesensor unit according to the fourth embodiment may be applied to each ofthe aforementioned first to third embodiments and after-mentioned fifthto eighth embodiments.

FIFTH EMBODIMENT

With reference to FIGS. 11 and 12, a fifth embodiment of the presentinvention will be specifically described below. As shown in FIGS. 11 and12, in a sensor unit according to the fifth embodiment, a tubularportion 12 having substantially the same inner diameter as that of athrough-hole 7 b, or a tubular protrusion, is integrally formed in amolded body 8 through a molding method in such a manner as to extend apressure-introducing passage 7. The remaining structures are the same asthose in the second embodiment, and their description will be omitted.

In the sensor unit according to the fifth embodiment, the tubularportion 12 is integrally formed with the molded body 8 to extend thepressure-introducing passage 7. Thus, for example, when a circuit boardhaving the sensor unit mounted thereon is entirely sealed with siliconeresin or the like to provide a moisture resistance thereto, the tubularportion 12 can prevent the silicone resin or the like from getting intothe pressure-introducing passage 7. The tubular portion 12 can alsoprevent foreign matter, such as foreign particles or dusts, from gettinginto the pressure-introducing passage 7.

SIXTH EMBODIMENT

With reference to FIGS. 13 and 14, a sixth embodiment of the presentinvention will be specifically described below. As shown in FIGS. 13 and14, in a sensor unit according to the sixth embodiment, apressure-sensor mounting portion 9 of a lead 4 is formed with foursmall-diameter channels 7 c for transmitting an external pressure to apressure-receiving portion 6. Thus, these small-diameter channels 7 cand a through-hole 7 b formed in an upper molded body 8 b define fourpressure-introducing passages 7. The remaining structures are the sameas those in the second embodiment, and their description will beomitted.

In the sensor unit according to the sixth embodiment, the foursmall-diameter channels 7 c or pressure-introducing passages 7 eachhaving a small diameter can prevent foreign matter, such as foreignparticles or dusts, from getting into a pressure sensor 1 through thepressure-introducing passages 7. In addition, even if an excessivepressure is introduced into the through-hole 7 b, the fourpressure-introducing passages 7 each having a small diameter reduces theshock due to the pressure. This can prevent breakage of the pressuresensor due to the excessive pressure.

While the sensor unit according to the sixth embodiment has four of thesmall-diameter channels 7 c or pressure-introducing passages 7, thenumber of the small-diameter channels 7 c is not limited to four. Thatis, any plural number of small-diameter channels 7 c orpressure-introducing passages 7 may be formed to obtain the same effect.Further, a plurality of pressure-introducing passages 7 may be definedby combining a plurality of small-diameter channels 7 c with a pluralityof independent through-holes 7 b-formed relative to the respectivesmall-diameter channels 7 c. The above characteristic structure in thesensor unit according to the sixth embodiment may be applied to theaforementioned fifth embodiment.

SEVENTH EMBODIMENT

With reference to FIG. 15, a seventh embodiment of the present inventionwill be specifically described below. As shown in FIG. 15, in a sensorunit according to the seventh embodiment, each of a plurality of leadterminals 4 a has an edge formed as a joint surface 4 b to be solderedto a circuit board 13 consisting of a printed board. The joint surface 4b and the bottom surface of a molded body 8 are spaced apart from oneanother by a given distance vertically (in the thickness direction ofthe molded body 8). The joint surface 4 b is formed by bending the leadterminal 4 a in a direction parallel to the side surface of the moldedbody 8 and then bending the edge of the bended lead terminal 4 a outwardrelative to the molded body 8 and in a direction parallel to the bottomsurface of the molded body 8. Each of the joint surfaces 4 a is joinedto the circuit board 13 through soldering. The remaining structures arethe same as those in the second embodiment, and their description willbe omitted.

In the sensor unit according to the seventh embodiment, each of thejoint surfaces 4 a is formed to have a given distance relative to thebottom surface of the molded body 8. This prevents the contact between alower molded body 8 b and the circuit board 13 during an operation ofjoining the sensor unit to the circuit board 13. That is, only the jointsurfaces 4 b are brought into contact with and soldered to the circuitboard 13. Thus, even if the circuit board 13 is deformed, adverseaffects due to the deformation can be suppressed. The abovecharacteristic structure in the sensor unit according to the seventhembodiment may be applied to each of the aforementioned first to sixthembodiments and an after-mentioned eighth embodiment.

EIGHTH EMBODIMENT

With reference to FIG. 16, an eighth embodiment of the present inventionwill be specifically described below. As shown in FIG. 16, in a sensorunit according to the eighth embodiment, a lead 4 has a pressure-sensormounting portion 9, and a device mounting portion. 14 formed byintegrating an acceleration-sensor mounting portion and asignal-processing-circuit mounting portion. A signal-processing circuit3 is disposed on the top surface of the device mounting portion 14, andan acceleration sensor 2 is disposed on the bottom surface of the devicemounting portion 14. That is, the device mounting portion 14 of the lead4 is sandwiched between the signal-processing circuit 3 and theacceleration sensor 2. The remaining structures are the same as those inthe second embodiment, and their description will be omitted.

In the sensor unit according to the eighth embodiment, thesignal-processing circuit 3 and the acceleration sensor 2 are disposedon the top and bottom surfaces of the lead 4, respectively. This allowsthe sensor unit to be reduced in size. In addition, the lead 4 made ofmetal, such as iron-nickel alloy, is interposed between thesignal-processing circuit 3 and the acceleration sensor 2. Thus, thelead 4 can prevent the acceleration sensor 2 from being adverselyaffected by noises of the signal-processing circuit 3. The abovecharacteristic structure in the sensor unit according to the eighthembodiment may be applied to each of the aforementioned second toseventh embodiments.

While the present invention has been described in conjunction withspecific embodiments thereof, various modifications and alterations willbecome apparent to those skilled in the art. Therefore, it is intendedthat the present invention is not limited to the illustrativeembodiments herein, but only by the appended claims and theirequivalents.

INDUSTRIAL APPLICABILITY

As mentioned above, the sensor unit of the present invention is useful,particularly, to the measurement of a plurality of physical quantities,and suitable for use as a sensor for detecting a plurality of physicalquantities, such as a tire-air-pressure sensor for measuring pressureand acceleration.

1. A sensor unit comprising: a lead having edge portions formed as lead terminals serving as input/output terminals; a plurality of physical-quantity sensors including a pressure sensor and an acceleration sensor, wherein each of said plurality of physical quantity sensors are disposed relative to said lead; a signal-processing circuit disposed relative to said lead and adapted to process a signal from each of said physical-quantity sensors; a molded body made of a plastic material, and formed to seal said lead, said physical-quantity sensors and said signal-processing circuit in such a manner as to allow said lead terminals to protrude outside said molded body, said molded body comprising a through-hole extending upwardly from a pressure receiving portion of the pressure sensor and allows fluid communication between the outside of the molded body and the pressure receiving portion; and wherein said signal-processing circuit is operable, based on the signal from at least one of said plurality of physical-quantity sensors, to control the ON/OFF action of the remaining physical-quantity sensors.
 2. The sensor unit according to claim 1, wherein: said pressure sensor, said acceleration sensor and said signal-processing circuit are disposed to form a line in the longitudinal direction of said sensor unit; said pressure sensor and said acceleration sensor are disposed at respective symmetrical positions with respect to the center of said signal-processing circuit in the longitudinal direction of said sensor unit; and each of said pressure sensor and said acceleration sensor has substantially the same height dimension.
 3. The sensor unit according to claim 1, further comprising a flexible resin interposed between a lower surface of said acceleration sensor and a surface of said molded body.
 4. The sensor unit according to claim 1, wherein said pressure-introducing passage includes a plurality of small-diameter channels.
 5. The sensor unit according to claim 1, wherein said molded body is integrally formed with a tubular portion extending continuously from the edge of the opening of said through-hole to the outside of said molded body and having substantially the same inner diameter as that of said through-hole.
 6. The sensor unit according to claim 1, wherein said plurality of physical-quantity sensors further include a rotational-angular-velocity sensor.
 7. The sensor unit according to claim 1, wherein: each of said plurality of physical-quantity sensors has substantially the same height dimension; and said molded body has a portion extending between each of said physical-quantity sensors and an outer surface of said molded body on the side of said physical quantity sensor, and another portion extending between said lead and an outer surface of said molded body on the side of said lead, each of said portions having substantially the same thickness dimension.
 8. The sensor unit according to claim 1, wherein said molded body have a portion covering the top-surface side of said lead and another portion covering the bottom-surface side of said lead, said portions being formed to have different tapered shapes from one another so as to allow the respective volumes of said portions to be substantially equalized.
 9. The sensor unit according to claim 1, wherein at least one of said plurality of physical-quantity sensors and said signal-processing circuit are disposed, respectively, on the top and bottom surfaces of said lead in such a manner as to sandwich said lead therebetween.
 10. A sensor unit comprising: a lead having edge portions formed as lead terminals serving as input/output terminals; a plurality of physical-quantity sensors including an acceleration sensor and a rotational angular-velocity sensor, each of said plurality of physical quantity sensors disposed relative to said lead; a signal-processing circuit disposed relative to said lead and adapted to process a signal from each of said physical-quantity sensors; and a molded body made of a plastic material, and formed to seal said lead, said physical-quantity sensors and said signal-processing circuit in such a manner as to allow said lead terminals to protrude outside said molded body, wherein said signal-processing circuit is operable, based on the signal from at least one of said plurality of physical-quantity sensors, to control the ON/OFF action of the remaining physical-quantity sensors.
 11. A sensor unit comprising: a lead having edge portions formed as lead terminals serving as input/output terminals; a plurality of physical-quantity sensors each disposed relative to said lead and adapted to measure a physical quantity; a signal-processing circuit disposed relative to said lead and adapted to process a signal from each of said physical-quantity sensors; a molded body made of a plastic material, and formed to seal said lead, said physical-quantity sensors and said signal-processing circuit in such a manner as to allow said lead terminals to protrude outside said molded body, wherein said signal-processing circuit is operable, based on the signal from at least one of said plurality of physical-quantity sensors, to control the ON/OFF action of the remaining physical-quantity sensors, and wherein each of said plurality of physical-quantity sensors has substantially the same height dimension; and said molded body has a portion extending between each of said physical-quantity sensors and an outer surface of said molded body on the side of said physical quantity sensor, and another portion extending between said lead and an outer surface of said molded body on the side of said lead, each of said portions having substantially the same thickness dimension.
 12. A sensor unit comprising: a lead having edge portions formed as lead terminals serving as input/output terminals; a plurality of physical-quantity sensors each disposed relative to said lead and adapted to measure a physical quantity; a signal-processing circuit disposed relative to said lead and adapted to process a signal from each of said physical-quantity sensors; and a molded body made of a plastic material, and formed to seal said lead, said physical-quantity sensors and said signal-processing circuit in such a manner as to allow said lead terminals to protrude outside said molded body, wherein said signal-processing circuit is operable, based on the signal from at least one of said plurality of physical-quantity sensors, to control the ON/OFF action of the remaining physical-quantity sensors, and wherein said molded body has a portion covering the top-surface side of said lead and another portion covering the bottom-surface side of said lead, said portions being formed to have different tapered shapes from one another so as to allow the respective volumes of said portions to be substantially equalized.
 13. A sensor unit comprising: a lead having edge portions formed as lead terminals serving as input/output terminals; a plurality of physical-quantity sensors each disposed relative to said lead and adapted to measure a physical quantity; a signal-processing circuit disposed relative to said lead and adapted to process a signal from each of said physical-quantity sensors; and a molded body made of a plastic material, and formed to seal said lead, said physical-quantity sensors and said signal-processing circuit in such a manner as to allow said lead terminals to protrude outside said molded body, wherein said signal-processing circuit is operable, based on the signal from at least one of said plurality of physical-quantity sensors, to control the ON/OFF action of the remaining physical-quantity sensors, and wherein at least one of said plurality of physical-quantity sensors and said signal-processing circuit are disposed, respectively, on the top and bottom surfaces of said lead in such a manner as to sandwich said lead therebetween. 